(1) Field of the Invention
The present invention relates to an instrument for production of a semiconductor device as well as to a process for producing said instrument.
(2) Description of the Prior Art
The production of a semiconductor device consists of many steps and consequently, various instruments are used for each production steps. However, conventional instruments have some problem.
A Jig for Semiconductor Device
For example, in the steps for semiconductor element production, such as a plasma etching step, epitaxy step and the like, it is very important that when a semiconductor wafer makes contact with, for example, a jig used in the steps, the semiconductor wafer is neither stained nor damaged and the properties of the resulting semiconductor device are not impaired.
The semiconductor wafer, therefore, is handled very carefully. For example, when the semiconductor wafer is transferred from one step to the next step, the semiconductor wafer is supported by a jig for transfer, such as a wafer hand, wafer holder or the like.
These jigs for semiconductor wafers have heretofore been made of a material such as metal, silicon carbide, silicon oxide, zirconium oxide, Teflon (Trademark) or the like. The jigs made of such materials have caused various problems when contacted with semiconductor wafers.
For example, metals each become a direct staining source for a semiconductor wafer; silicon oxide and zirconium oxide each have a high hardness, are difficult to process, damage the semiconductor wafer, and are expensive; silicon carbide has a high hardness, is difficult to process in high precision, has a low material purity, and causes staining; and Teflon has a problem in purity of material and is difficult to obtain in a high purity.
A Semiconductor Wafer Dummy
As semiconductor integrated circuits have become finer, have a higher integration and a higher density, a plasma etching technique capable of forming a more precise and finer pattern has become more necessary. In this plasma etching, a high-frequency electric current is applied between electrodes to generate a plasma, and a silicon wafer is etched by the plasma. The free radicals and ions of halogen-based gas present in the plasma are attracted by the electric field inside an etching chamber and hit the wafer placed on the opposing electrode, whereby the wafer is etched.
When the above etching is repeated in the chamber of a plasma etching apparatus, the etched silicon and other substances are deposited and adhered on the chamber inside wall, the wafer holder, etc. Therefore, the removal of the deposited or adhered silica, etc. by cleaning becomes necessary. Currently, however, this cleaning is done manually and is generally conducted by wiping off the silicon, etc. by using, for example, a special cloth for a semiconductor device.
The above manual cleaning by using, for example, a special cloth for a semiconductor device to wipe off the silicon, etc. requires a long time in a cleaning operation and includes a high possibility of secondary staining with human sweat. For these reasons, development of a new cleaning method has become necessary.
In order to solve the above problems, there was proposed a method which comprises fixing, in a plasma etching chamber, a material resistant to plasma etching as a dummy for a wafer, and generating a plasma in the chamber to remove the deposited silicon, etc. by etching. As the material resistant to plasma etching, usable as a dummy for a wafer, there were studied quartz, silicon carbide, graphite and the like.
However, these materials have problems. That is, quartz cannot be used as a dummy because of insulation; silicon carbide is expensive and is difficult to process and obtain at a high purity; and graphite has a detrimental drawback of powder detachment and cannot be used as a dummy although it is inexpensive and can easily be processed and obtained at a high purity.
Boats for Supporting Semiconductor Wafers
Boats for supporting semiconductor wafers are used for various purposes such as (1) supporting of semiconductor wafers thereon, (2) prevention of detachment of said wafers in a diffusion treatment in diffusion furnace and (3) transfer of said wafers before and after diffusion treatment. As semiconductor devices have become integrated more highly and have come to possess higher performances in recent years, a necessity has become greater for a boat for supporting semiconductor wafers which is resistant to a heat treatment at high temperatures and which can be produced easily at a high purity.
Conventional boats for supporting semiconductor wafers include, for example, a boat described in Japanese Patent Application Rokai (Laid-Open) No. 60-107843. In this boat, however, since the constituent members are made of quartz or silicon, strain, cracking and chipping occur during the formation of grooves (e.g. rod grooves for supporting wafers); as a result, semiconductor wafers are rubbed against the defective portions of rods, resulting in generation of dust, damaging of wafers, and appearance of dislocation defects in wafers.